Lead

Lead has many uses . Therefore it is valuable resource mined all over the world . But just like any other substance mined and excavated from underneath the ground , lead mining causes a significant amount of pollution

In the book written by Jose S . Casas , Lead : Chemistry , Analytical Aspects , Environmental Impact and Health Effects ‘ the author tries to strive the balance in describing the element which is popularly designated as Pb in the Periodic Table of Elements . On one extreme Casas was raving about the benefits and the multiple applications that can [banner_entry_middle]

be had with using lead . On the other hand , Casas is lamenting the environmental impact caused by the mining of the same

Occurrence

Casas began by explaining the basics . He made the following remarks as with regards to how lead can be found naturally

Although lead can be found in nature as the pure element , this is extremely rare and it is usually present as PB (II ) in deposits with different origins . In these sources it is combined with other elements such as sulphur and oxygen in a variety of minerals that have a wide range of compositions (p .17

Casas added that Argentiferous galena is , .by far the most important lead mineral , commonly contains microscopic bodies of silver-rich minerals (p .170 . But Casas was quick to add that aside from galena and other sulphides lead can be found in minerals such as : a ) cerussite (PBCO2 b ) anglesite (PbSO4 c ) litharge /massicot (PbO and d minimum (Pb3O4 ) – these are regularly used in the production of lead

Fig . 1 Argentiferous galena (most important lead mineral

Properties

Lead or Pb is a bluish-white lustrous heavy metal that can be seen in group 14 of the Periodic Table . The crystals of lead are face-centered cubic and have a short lead-lead distance of 3 .49 angstrom (p .24

The atomic properties of lead was well-covered in the discussion and Casas pointed out that Pb has four common stable isotopes and several radioactive isotopes and possessing half-lives longer than 10 hours (p .24

Comparing it to other metallic elements Casas asserted that

Lead has physical properties common to other metals : it has metallic lustre with shiny freshly cut surfaces , a high density , a low melting point , it is a conductor of electricity and heat and is soft , ductile and malleable (p .25

As mentioned luster is one of the physical properties of lead as it is a metal . But this luster does not stay very long when exposed to moist air and this is caused by the formation of a layer of lead (II ) oxide on the surface . This can further react with carbon dioxide to form lead (II carbonate

The good thing about this reaction is that the oxide and the carbonate acts as a shield protecting the core of the metal from outside forces